Conveyor belt with spiral overlay

Abstract: To facilitate pitch control and to avoid the rippling and misalignment of spirals of an overlay (10) of a conveyor belt, a pair of opposed elongate loops (32), preferably having a closed configuration, are arranged to co-operate between intermeshed linking bends (12). The elongate loops (32) have end surfaces that engage and therefore limit possible movement between adjacent connecting rods (14) that extend laterally across the conveyor belt and on which the spiral overlay (10) is supported. More particularly, the elongate loops (32) inhibit the relative movement of adjacent connecting rods towards one another and, as such, control and regulate the spacing between adjacent rods, as shown in Fig 3A.

Description: FIELD OF THE INVENTION The present invention relates to conveyor belts and to an overlay which forms a support surface for conveyor belts, particularly an overlay comprised of integral or moduler wire spirals forming various lift, edge guard and lane divider elements interconnected together by a system of connecting rods and connective links. More especially, the present invention relates to a mechanism for controlling the pitch between adjacent support rods. BACKGROUND OF THE INVENTION Wire conveyor belt systems are widely used in a great variety of industrial fields. A wire mesh overlay generally comprises the support surface of a wire conveyor belt, with the mesh overlay being formed of wire spirals intermeshed together by connecting rods which extend transversely across the width of the belt. Typically spiral overlays are comprised of interconnected flat spirals intermeshed and connected to one another by the rods. The ends of the rods are inserted into connective links which may also serve as tractive links around a sprocket wheel. One of the problems associated with a conventional spiral overlay is that generally the spirals have been designed without any provision for controlling the pitch of the spirals as the overlay winds around the sprocket wheel or around a turning section of the conveyor. The pitch is defined to be the distance between adjacent rods of a conveyor overlay. In operation, the pitch decreases when traversing a sprocket wheel on a straight run of a conveyor, and the pitch will vary along the width of the overlay as an overlay winds around a turning section or curve of the conveyor. Varying pitch is also experienced in the transition section of a conveyor between a straight run and curved portion. Whenever the pitch varies, however, without significant pitch control, adjacent spirals bunch up and causes the leading edge of one spiral to be vertically displaced from the trailing edge of an adjacent spiral. This displacement results in rippling of the overlay and misalignment of the spirals, and can lead to permanent distortion if the spirals are subject to bending and twisting stresses beyond their elastic limit. US Patent Nos 3,920,117 to Roinestad and 4,878,362 to Tyree, Jr. exemplify previous attempts to provide some measure of pitch control to spiral overlays. Both the Roinestad and Tyree patents provide spirals having upward indentations on their undersides to contain the rods in bent wire portions. Although the indentations may prevent some displacement of the rods toward each other, the bent wire portions do not provide as positive a pitch control as the elongated loops of the present invention which completely contain the rods therein and completely prevent the rods from touching each other. In contrast, the bent wire portions of the prior art spirals do not prevent the rods from touching each other entirely, especially in jam situations, the bending and twisting forces in the belt would still cause the rods to travel together and result in all loss of pitch control. Furthermore, forming indentations on each turn on the underside of the spiral is costly, difficult and involves more manufacturing steps, especially when using high tensile wire. Another problem associated with the use of a conventional spiral overlay is that generally no provision is made to prevent conveyed items from slipping on the support surface while the overlay traverses inclined portions of the conveyor. Prior attempts at solving the problem typically involved an additional manufacturing step. One of the ways was to fasten clips onto a completed overlay by crimping or welding. Another way was to rigidly attach solid bars of plates which traverse the overlay using screws. Extra attachment steps such as these result in higher cost and lower efficiency. Thus, there has been a need for an economical way of providing lift elements for added traction on the conveying surface of the overlay to prevent conveyed items from falling down an inclined section and bunching up on one portion of the overlays. In addition, when conveying small articles or articles that move about easily, there has been a need to provide edge guards along the side edges of the overlay in order to prevent the items from falling off of the conveyor altogether. Edge guards have also been provided in the past by rigidly securing plates to the overlay which also involved the extra step of attachment during manufacture. For articles which are measured or separated prior to loading onto the conveyor, there has been a need to divide the support surface of the overlay into pockets to contain and convey pre-measured quantities of articles or separated articles. US-A-2,734,283 relates to conveyor trays that have a base grid inclined with respect to a support chassis. The base grid is detachable with respect to the chassis, while the chassis has pins extending outwardly from its ends to support idler rollers that can engage a suitable track or conveyor system. WO-A-92/05096 relates to a belt overlay apparatus made up of wire coils that have U-shaped segments that provide an ovoid passageway through which support rods are inserted. The ovoid passageway is generally of an elaborate wire coil configuration and confines movement of the support rods within the passageway, but this configuration results in an expensive and heavy overlay. Furthermore, in relation to the U-shaped structure of the overlay (achieved through bending of the wire), significant force is exerted on the bent wire sections by the support rods when the overlay runs through a curve. Consequently, the overlay of WO-A-92/05096 is also deformed relatively easily and therefore fails to provide sufficient pitch control. SUMMARY OF THE INVENTION Accordingly, the present invention provides a conveyor belt and a wire spiral overlay for a conveyor belt which overcomes or mitigates many of the problems associated with the prior art. The present invention pertains to a spiral overlay having multiple variations, but generically, a spiral overlay is comprised of continuous wire spirals having intermediate pitch control means as defined in claim 1. The wire spirals are intermeshed together by connecting rods extending across the conveyor in the transverse direction. The ends of the rods are typically connected to connective links which pivotally connect adjacent rods, and are arranged along the side edges of the conveyor. The links may serve as tractive links, that is, they can engage the sprocket wheels which drive the conveyor. The links may also be made of wire similar to the wire spirals of the overlay. The spirals may incorporate tight coils or "pigtails" which receive the ends of the rods. The spirals may be simple flattened helixes with linking bends which intermesh with corresponding linking bends of adjacent spirals. The simple flattened helix shape of the spirals provides collapsibility of spirals connected by a rod, relative to one another. Allowing for collapsibility ensures that any variation in the pitch of the conveyor, such as at a curved section or near the sprocket wheel, is accommodated by the ability of the spirals to move relative to one another, especially those spirals operatively connected to a single rod. The first category of spirals of the present invention incorporate elongate loops between the opposed linking bends across the spiral for engagement to the rods of the conveyor. The elongate loops contain the rods in a manner that affords pitch control as the overlay winds around the sprocket wheel or a turning section. The spiral may be straight, that is of even width, for a straight-run conveyor in which case the elongate loops will be of constant width. Alternatively, the spiral may be tapered on one or both sides and incorporate double loops along its length or single loops along one side. The widths of the loops on a tapered spiral vary with the amount of taper, and the spiral may be tapered for a fixed turn conveyor. The widths of the elongate loops also determine the collapsibility of the spirals on the rods. In either the tapered or non-tapered spiral, the loops may be multiple loop coils for added strength. The spiral overlay constructed as described in the preceding paragraph enables pitch control which prevents the spirals from bunching up and prevents substantial vertical displacement of a leading edge of one spiral from the trailing edge of an adjacent spiral. The overlay enables the rippling and misalignment problems of the prior conveyors to be avoided. As will be appreciated by those skilled in the art, any number of coils or loops may be incorporated into the spirals to receive the rods, and the shape of the loops or coils determines some important characteristics of the finished overlay. Circular loops or coils will fix the position of the connecting rod on the spiral, whereas elongate loops will allow the rod to move within the loop, and thereby accommodate some movement of adjacent spirals relative to one another. The widths of the elongate loops determine the range of motion of the rod within the loop. Therefore, for straight runs, circular loops may be desired in order to fix the positions of the rods relative to one another, and thereby prevent the spirals from bunching up. Alternatively, loops of fixed width can be provided to allow control collapse around a sprocket. On the other hand, for turning sections or curves, elongate loops may be desired in order to allow the rods to vary their positions relative to one another to accommodate the spirals which will tend to flex and collapse into one another. Providing elongate loops which are integrally formed with the spiral is simpler, more efficient and economical than the prior art methods. The spirals are arranged relative to one another so that their linking bends are intermeshed with those of an immediately adjacent spiral. Connecting rods operatively connect pairs of adjacent spirals. Adjacent rods are typically connected by the connective links arranged along the side edges of the overlay. The connective links are generally U-shaped and are arranged such that the closed part of one link rests within the open part of an adjacent link. The connecting rods may pivotally interconnect the links through holes or slots on the legs of the U-shaped links. Each link suitably receives two rods, one near the closed part and the other near the open part. The connective links may alternatively be formed of wire similar to the spirals, or of flat plates and be connected in the same way as the U-shaped links. The present invention is further described by way of example only with reference to the accompanying drawings, in which: FIG. 1 is a top plan view of a spiral overlay section in accordance with a first preferred embodiment of the present invention. FIG. 2A is a top plan view of a portion of a double tapered spiral. FIG. 2B is a top plan view of a portion of a single tapered spiral. FIG. 2C is an end view of one end of a single spiral of the overlay of FIG. 1 according to the present invention. FIG. 2D is an end view of the other end of a single spiral of the overlay of FIG. 1 according to the present invention. FIG. 3A is a top plan view and cross section of the spiral section taken along line 3A-3A of FIG. 1. FIG. 3B is a top plan view and cross section of the spiral section taken along line 3B-3B of FIG. 1. FIG. 3C is a top plan view and cross section of the spiral section taken along line 3C-3C of FIG. 1 with the connective links removed. FIG. 3D is a top plan view and cross section of the spiral section taken along line 3D-3D of FIG. 1. FIG. 3E is a top plan view and cross section of the spiral section taken along line 3E-3E of FIG. 1. FIG. 3F is a top plan view and cross section of the spiral section taken along line 3F-3F of FIG. 1 with the connective links removed. FIG. 3G is a detailed view of a portion of the spiral overlay of FIG. 1. FIG. 4A is a detailed top plan view of a series of connective links of a partially assembled spiral overlay. FIG. 4B is a cross-section of the links taken along line 4B-4B of FIG. 4A. FIG. 4C is a partial cross-section of the links of FIG. 4A. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGS. 1-4, a spiral overlay section 10 connected to a section of a conveyor belt is depicted according to a first preferred embodiment of the present invention. The overlay section 10 will be referred to as the overlay for simplicity. The spirals of overlay 10 are preferably formed of high tensile metal wire, such as stainless steel wire. Examples of wire that can be used include ANSI Type 304 stainless steel, 0.047 inch diameter, 18 gauge, 267/295 KPSI tensile strength, and 0.062 inch, 16 gauge 258/285 KPSI tensile strength. The wire is bent to form overlay 10 in such a manner that a plurality of flat sections 11 extend generally in the lengthwise direction of the conveyor belt and are joined by opposed arcuate linking bends 12. A spiral 26 is thus formed of flat sections 11 and linking bends 12 formed integrally into a generally flat helix that extends across the width of the belt. Overlay 10 of FIG. 1 is for a conveyor belt designed to travel around curves and turns in a single direction, and is made up of tapered spirals having their linking bends 12 intermeshed and operatively connected by connecting rods 14 which extend across the conveyor in the transverse direction. Tapered spirals refers to the variance in length of each spiral across the width of the belt. Along the side edges, outside edge 16 and inside edge 18 of the overlay, connective links 20 are arranged, in a nested relationship to one another, extending in the longitudinal direction. Links 20 receive the ends of rods 14 to thereby pivotally interconnect the rods of overlay 10. As seen in detail in FIGS. 4A-4C, links 20 are generally U-shaped with a closed side 22 and an open side 24, and a generally circular aperture 21 forming a bearing surface on each leg of the link near the open side 24. Opposed slots 23, forming bearing surfaces, are disposed near the closed side 22, such that each rod 14 is pivotally retained in the circular apertures of one link 20 and the slots of an adjacent link. All of the links 20 are longitudinally expandable and collapsible by virtue of the slots within which rods 14 may freely pivot and move relative to one another, such that the overlay 10 is vertically flexible to pass vertically around suitable end pulleys or sprocket wheels. The ends of rods 14 are finished with buttonheads 15, and to maintain the rods in the links the rods may be fixed relative to the circular apertures 21 by a weld 25 toward the exterior of the link, and a weld 27 toward the interior of the overlay. Welds 25 and 27 do not affect the movement of the rods in slots 23 however. A conveyor belt of a desired length is formed by assembly rods 14, links 20 and overlay 10. Overlay 10 can be used with belts of the type disclosed in U.S. Patent Nos. 3,920,117; 4,078,655 and 4,940,133, the disclosures of which are hereby incorporated by reference. Alternatively, flat plate links of the type disclosed in FIGS. 6-8 of U.S. Patent No. 4,078,655 and referred to with reference numerals 78 and 80 may be used in place of U-shaped links 20. Overlay 10 is comprised of tapered spirals 26. Each spiral 26 has a double taper, meaning that both the leading edge 28 and trailing edge 30 are tapered when viewed in plan view. FIGS. 2A and 2B illustrate short sections of spirals having a double and single taper respectively. The spirals in FIGS. 2A and 2B do not represent spiral 26 of FIG. 1, but are included to simply illustrate types of tapers. In both tapered spirals, the width of the spiral increases from one end across to the other end. The taper of the spiral closely conforms to the maximum separation between adjacent rods. The leading edge 28 and the trailing edge 30 of a double taper spiral as in FIG. 2A are tapered across the width of the spiral. In contrast, a single taper spiral as in FIG. 2B has a leading edge 28 which is tapered, a trailing edge 30 which is straight across the width of the spiral. The choice between double taper or single taper spirals would depend upon variables such as the curvature of the overlay section and the amount of collapsibility desired between the rods. The end views of spiral 26, of the overlay of FIG. 1, are shown in FIGS. 2C and 2D, with FIG. 2C illustrating the wider end and FIG. 2D illustrating the shorter end. Incorporated within the flattened helical structure of spiral 26 are elongated loops 32 which are preferably arranged in opposed relationship along a single section of linking bends, i.e., at opposite end of a single flat section 11. The lengths of elongated loops 32 determine the distance through which the rods 14 can move, thereby providing pitch control to the overlay. Elongated loops 32 preferably are proportionally sized along the tapering length of spiral 26 to accommodate the curve of the conveyor. Although spirals 26 of FIG. 1 have two sets of opposed elongate loops 32, one central set indicated as 32', and a set at the outer side indicated as 32", many variations on the positioning of the loops are possible. For instance, each and every linking bend may incorporate an elongated loop, the linking bends adjacent the inner side of the belt may also have elongated loops, only linking bends at the ends of the spiral may include elongated loops, or the elongated loops may be spaced apart and not on a single section of linking bends. For example, the spiral of FIG. 2B has pigtail loops only along the trailing edge of every sixth bend. Pitch control that is provided by elongated loops 32 is illustrated in FIGS. 3A-3F in which adjacent rods 14 are shown with a section of a spiral 26 operatively connecting the rods. The exemplary belt in FIG. 1 and FIGS. 3A-3G is designed to function as a space-saver belt where the inside edge 18 of the belt is prevented from collapsing, as disclosed in U.S. Patent No. 4,940,133. In FIGS. 3A-3C, the belt is shown proceeding in a straight line direction when rods 14 are parallel to one another and all at the same first pitch. In FIGS. 3D-3E, the belt is shown proceeding around a lateral curve. In this type of belt, the inside edge 18 of the belt remains at the same first pitch, as seen by the equal rod spacing in FIGS. 3C and 3F, and the outside edge 16 of the belt expands to a second larger pitch, as seen by comparing the rod spacing in FIGS. 3A and 3D. The spiral sections shown include the opposed elongated loops 32. The position of the rods within the elongated loops determines the distance they are apart, which consequently determines whether adjacent spirals are expanded or collapsed with respect to one another. As seen in FIG. 3A, when adjacent rods almost bear on the innermost bearing surfaces 34 of the elongated loops 32, the spirals are at their maximum contraction. Since the overlay of FIG. 1 is a tapered overlay. The amount of contraction and expansion across the width of the overlay will vary to accommodate the tapering spirals. As seen in FIGS. 3B and 3C, the adjacent rods 14 are in different positions relative to the elongated loops 32, even though at that point the overlay is at its maximum contraction. Similarly, FIGS. 3D-3F show a spiral in a section of the overlay which is more expanded than that shown in FIGS. 3A-3C, and the rods are disposed toward the outermost bearing surfaces 36. When adjacent rods 14 bear on the outermost bearing surfaces 36 of the elongated loops 32, the spirals are at their maximum expanded position. The amount of expansion or contraction is determined by the position of the rods within the elongated loops. FIG. 3G is a detailed view of two adjacent rods connecting intermeshed spirals 26. Spirals 26 in FIG. 3G are slightly collapsed relative to one another. If the belt were totally expanded, the rods would bear directly on the inner surfaces of the linking bends. As mentioned above, the inside edge 18 of the belt illustrated in FIG. 1 remains at a constant pitch. Pitch control loops are thus not provided along the inside edge of the belt. However, if the inside edge of the belt is to collapse, such as in the belt disclosed in U.S. Patent No. 4,078,655, pitch control loops would preferably be located adjacent the inside edge of the belt. Pitch control loops can also be provided at appropriate locations across the width of belts designed to travel around lateral curves in two directions, or in belts designed for straight line travel such as disclosed in U.S. Patent No. 3,920,117. In general, a single spiral has one or both of its ends, those last bends adjacent the side edges of the overlay, finished in some manner. The finishing is generally accomplished by forming a coil or loops, referred to as a pigtail at the end of the wire. In the FIG. 1 embodiment, pigtails 38 of each spiral are shown spaced from the rod at the leading edge 28 of the spiral forward of the leading edge rod on the inside of the belt and rearward on the inside. In the FIG. 5 embodiment, each spiral has a pigtail 38 fixed at its ends to a single rod at its leading edge 28. This in turn allows the trailing edge 30 of the spiral to intermesh with the rod at its trailing edge. The collapsibility of one spiral, therefore, is permitted only on one side in regard to any two adjacent rods since the pigtails are only on the leading edge. However, since each spiral is also intermeshed with another adjacent spiral at its trailing edge, the effect of a continuous spiral overlay is that all the spirals can collapse in either direction relative to the rods. The spiral overlay of the present invention, in any of its embodiments, employs a conventional drive system with the connective links 20 serving as tractive links which can engage a sprocket or an idler pulley. The overlay of the present invention is therefore, readily adaptable for use on existing conveyor systems by simply replacing an existing overlay with the spiral overlay of the present invention. Components of the overlay/belt such as the connective links and rods are of conventional design. The spiral overlay of the present invention can also be used in spiral conveying systems of the type disclosed in U.S. Patent No. 4,940,133. The wire spirals of the present invention can be formed on CNC spring coilers or wire forming machines such as available through BHS-Torin, Inc. of Farmington, Connecticut; Automated Industrial Motion of Muskegon, Michigan and Simplex Rapid of Milan, Italy. Although the present invention has been illustrated in terms of preferred embodiments, it will be evident that numerous changes, adaptations, and modifications may be made without departing from the scope of the invention which is to be limited only by the appended claims.

Claims: A spiral overlay (10) for a conveyor belt formed of a plurality of connecting rods (14) extending laterally across the belt, the belt having an upper conveying surface, a lower surface and side edges (16, 18) said overlay comprising: a plurality of wire spirals (26) each forming a generally flat helix extending across the belt, each of said spirals including opposed arcuate linking bends (12) at locations across each said spiral, said spirals being arranged relative to one another such that said linking bends (12) are intermeshed with linking bends of an immediately adjacent one of said spirals, and said intermeshed linking bends of adjacent spirals being adapted to receive one of the rods to operatively connect said spirals; and at least one pitch control means for controlling the spacing between adjacent ones of the rods (14), characterised in that each wire spiral extends continuously across substantially the entire width of the belt and said pitch control means is part of said wire spiral and is located intermediate said side edges of the belt and comprises at least a pair of opposed elongate loops (32) which are closed loops arranged between said linking bends so as to coincide with said intermeshed linking bends (12) and said elongate loops (32) having end surfaces to limit movement of adjacent ones of the rods toward each other to control the spacing therebetween, wherein each closed loop entirely surrounds an associated rod. The overlay of claim 1, wherein the belt is adapted to travel around lateral turns and said wire spirals are tapered such that the spacing between said opposed arcuate linking bends increases from one side of the belt to the other side of the belt. The overlay of claim 2, wherein each set of said elongate loops along said tapered wire spiral is proportionally sized according to the distance between said opposed linking bends and said pitch control means includes: (i) a set of said opposed elongate loops on each opposed set of said linking bends; or (ii) a set of said opposed elongate loops on intermittent ones of said linking bends. The overlay of claim 1, 2 or 3, wherein said pitch control means includes: (i) a set of said opposed elongate loops (32) on each opposed set of said linking bends; or (ii) a set of said opposed elongate loops on intermittent ones of said linking bends. The overlay of any of claims 1 to 4, wherein said spirals are formed of high tensile metal wire. The overlay of any of claims 1 to 5, wherein said pitch control means is located substantially centrally between the side edges of the belt. A conveyor belt having an upper conveying surface, a lower surface and side edges, said belt comprising: a plurality of connecting rods (14) extending laterally across the belt; a spiral overlay (10) as claimed in any preceding claim wherein said intermeshed linking bends of adjacent spirals receive one of said rods to operatively connect said spirals and a plurality of connective links arranged at the ends of said spirals of operatively connecting said rods. The conveyor belt of claim 7, wherein said connective links are formed of an integral length of wire and include substantially circular loops at the ends of said wire toward a trailing side of said belt and an elongate loop substantially centrally disposed on said wire toward a leading side of said belt. The conveyor belt of any of claims 7 or 8, wherein said links are formed of high tensile metal wire.

Inventors: KUCHARSKI JOHN G, KUCHARSKI, JOHN G.
Applicants: ASHWORTH BROS INC, ASHWORTH BROS. INC.
Application year: 1994
Main classification: B65G17
IPC codes: B65G17